Method of making thread protector and product obtained



June 19, 1962 F. J. KENNEDY 3,039,187

METHOD OF MAKING THREAD PROTECTOR AND PRODUCT OBTAINED 2 Sheets-Sheet 1 Filed Dec. 17, 1956 S INVENTOR.

AT T0 R NEYS F. J. KENNEDY 3,039,187

June 19, 1962 METHOD OF MAKING THREAD PROTECTOR AND PRODUCT OBTAINED 2 Sheets-Sheet 2 Filed Dec. 17, 1956 INVENTOR.

BY w W W w W b ATTORNEYS United States Patent 3,039,187 METHOD OF MAKING TAD PROTECTOR AND PRODUCT OBTAINED Frank J. Kennedy, Pittsburgh, Pa., assignor, by mesne assignments, to H. K. Porter Company, Inc., Pittsburgh,

Pa., a corporation of Delaware Filed Dec. 17, 1956, Ser. No. 628,762 6 Claims. (Cl. 29-534) This invention relates to the thread protectors which are screwed over the ends of pipes to protect the threads in shipment, storage, and subsequent handling prior to actual use.

Pipes are commonly sold in standard lengths and with both ends threaded. A coupling is ordinarily supplied with each pipe and this coupling is screwed over the threads at one end of the pipe. Protection is needed for the threads on the other end, and it is usual to have some kind of inexpensive fitting which is used only for the purpose of protecting the threads prior to the time that the pipe is brought to the location Where it is to be used.

For moderate and large sizes of pipe, thread protectors of sufficient strength to protect the threads adequately have been of such high cost that economic considerations required that they be returned to the pipe mill for reuse.

This has not always been satisfactory because it entails the inconvenience and cost of gathering and shipping discarded protectors and the expense of reconditioning those damaged in service.

It is an object of this invention to provide a method of making thread protectors from less expensive stock and at greatly reduced labor cost. The thread protectors made in accordance with this invention are of such reduced cost that when made of light gage stock they can be scrapped after one use.

Another object of the invention is to provide an improved method for making thread protectors from flat stock and with a minimum of hand labor. The method preferably includes the use of a multi-slide machine for cutting, shaping and bending the stock to make the protector.

Another object is to provide a thread protector of such construction that it can be made on a multi-slide machine and by the method of this invention.

Other objects, features, and advantages of the invention will appear or be pointed out as the description proceeds.

In the drawing, forming a part hereof, in which like reference characters indicate corresponding parts in all the views;

FIGURE 1 is a diagrammatic top view, mostly in section, showing a multislide machine equipped for performing most of the steps for making thread Protectors in accordance with this invention;

FIGURE 2 is greatly enlarged side view showing the strip after it has been punched at the first work station of the apparatus shown in FIGURE 1;

FIGURE 3 is an enlarged, transverse sectional view showing the position of the strip and adjacent parts at the second work station of the apparatus shown in FIG- :parts after the die has closed;

work stations.

Patented June 19, 1962 "ice FIGURE 7 is a greatly enlarged diagrammatic view showing the way in which the strip is formed around a post and the way in which the fiange is held during the bending of the strip around the post;

FIGURE 8 is a sectional View, on a reduced scale from FIGURE 7, showing the way in which the edges of the strip are secured together after removal from the apparatus shown in FIGURE 1 and FIGURE 9 is a sectional view showing the completed thread protector, but with a modified type of seam from that shown in FIGURE 8. The thread protectors of this invention are preferably made from strip stock which is supplied in a reel 11. The strip material is metal and preferably hot rolled steel, this being a satisfactory and economical material for the thread protector. Eighteen carbon steel has been found to be particularly satisfactory but this is described merely as an illustration, and the invention is not limited to such steel, and may even use other kinds of metal such as strip aluminum. 'It is, of course, necessary that the material be malleable. The height and thickness of the strip depends upon the size of the thread protector to be made and upon the depth of threads and mechanical strength desired in the final product.

The metal strip as it comes from the reel 11 is indicated by the reference character '12. It is advanced through the apparatus with .a step-by-step movement. Any suitable apparatus for this purpose can be used. The drawing shows a clutch 14 in a slide block 15 which runs along a guideway 16. The clutch 14 and slide block 15 are reciprocated back and forth along the guideway 16 by a cam 18 having a groove therein. A cam follower 20, extending from the clutch 14, fits into the groove of the cam 18.

The cam 18 is supported by an axle 22 extending through a bearing 24. The axle 22 is rotated by a worm wheel 26 driven by a worm 28 on a main drive shaft 30. A motor 32 rotates the main drive shaft 30. The feed mechanism described is merely representative of step-bystep mechanism for advancing the strip 12 successively by uniform strokes.

The strip 12 is fed to a first work station designated generally by the reference character 35. At this work station 35, a punch 36 is reciprocated back and forth in a bearing 37 by a groove cam 38 on a drive shaft 39. This drive shaft is driven by a worm wheel 26 meshing with a worm 28 on the main drive shaft 30. There is a die 42 on the other side of the strip from the punch 36 and the die 42 has a recessed face 44 for receiving the punch 36. The cam 38 operates in timed relation with the feed mechanism so that the punch 36 advances against the strip 12 during a portion of the cycle when the strip is stationary.

In the preferred operation of the invention, the punch 36 notches the strip 12 as shown in FIGURE 2. Notches 47 and 48 are punched in the upper and lower edges, respectively, of the strip 12; and an opening 50 is punched through the mid portion of the strip. This opening 50 is shaped so that a dove tail tab 52 is left at one side of the opening 50 and a dove tail cut-out 54 is left on the other side of the opening. The two portions of the strip that are left between the opening 50 and the top and bottom notches 47 and 48 are for the purpose of keeping the strip in one piece during its travel through subsequent This permits better control of the strip and also permits it to be effectively fed through all work stations by a single feed mechanism. At the end of the work stations these sections of strip between the opening as 50 and the top and bottom notches 47 and 48 are removed, as will be more fully explained.

One step of the feed mechanism advances a cut-out portion of the strip from the punch 36 to the left-hand end of a second Work station 55. The next operation of the feed mechanism advances the length of strip behind this cut-out into the work station 55, the length of the work station being equal to the length of the feed stroke which is in turn equal to the length of strip to be used for making one thread protector.

At the work station 55 there is a die consisting of a relatively fixed element 57 and a movable element 58. The movable element is attached to and guided by dowels 60 which slide in bearings in a fixed frame 62. The movable die element 58 is advanced against the relatively fixed die element 57 by a cam 64. There are springs 66 for bringing the movable die element 58 back as the cam 64 continues to rotate. The cam 64 is secured to a shaft 68 rotated by a worm wheel 26 which meshes with a worm 28 on the main drive shaft 30. The cam 64 advances the movable die element 58 to force the strip against the relatively fixed die element 57 at the time in the cycle when the strip 12 is stationary.

FIGURE 3 shows the strip 12 against the die element 57 and held against upward movement by a guide 70 attached to the die element 57. The movable die element 58 has a spring loaded hold-down 72 and a forming punch 74. As the movable die element 58 moves toward the relatively fixed die element 57, the hold down 72 comes into contact with the strip 12 first and holds the strip firmly in position. The form punch 74 advances into contact with the lower part of the strip 12 and forms it to the contour of the die elements 57 and 58, as shown in FIGURE 4.

Thus the strip 12, after operation of the die at the second work station, has its lower end portion bent inwardly to form a flange 75. This flange 75 extends along the full length of each part of the strip which is to be used to make a thread protector, that is, the flange 75 extends for the full length of each blank.

Beyond the second work station 55 (FIGURE 1) there is a third work station 76. This work station includes a relatively fixed die element 77 and a movable die element 78 supported by dowels 80 which slide in bearings in a fixed frame 82.

The movable die element 78 is advanced toward the relatively fixed die element 77 by a cam 84, and the movable die element 78 is retracted by springs 86. The cam '84 is secured to a drive shaft 88 driven by a worm wheel 26 meshing with a worm 28 on the main drive shaft 30.

FIGURE shows the contour of the die elements 77 and 78. The relatively fixed die element 77 is shaped so that the flange 75 extends'under a clearance provided for the purpose. The movable die element 78 has a spring-loaded hold-down 90 which is shaped to contact with the flange 75 and the portion of the strip 12 just albove the flange 75. The movable die element 78 also has a formed punch 92 with a contour complementary to that of the relatively fixed die element 77. After the spring-loaded hold-down 90 has gripped the lower portion of the strip 12, further advancing movement of the movable die element 78 causes the formed punch 92 to deform the strip 12 to the contours of the die element 77 as shown in FIGURE 6.

Thus when the strip 12 leaves the third work station, the portion of the strip above the flange 75 has a cross section which may be described as concavo convex. In the construction shown, the cross section of the surface of the strip is bounded by straight lines which meet in angular relation but the exact shape is not critical and the concave-convex cross section may be generally curved instead of having the straight angular relation illustrated; but it is desirable to have the intermediate portion of the strip generally straight so as to obtain a substantially uniform diameter for a portion of the length of the throat 4 in the finished thread protector. It is the throat which is threaded in the final product, and this makes the c0nstant diameter of the middle portion of the formed thread protector desirable.

The next step of advancement of the strip 12 carries the blank in the work station 76 to a location where the forward end of the blank is between a punch 97 on one side of the strip and a die 98 on the other side of the strip. The punch 97 is stationary, being connected with a fixed frame 100; and the die 598 is moved toward and from the punch to displace the strip 12 against the punch. This movement of the strip causes the punch to sever the strip by punching out the two remaining parts of the strip above and below the opening 50 (FIG- URE 2).

The die 98 slides in bearings in a fixed frame 102. A cam 104 advances the die 98, and a spring 186 retracts the die. The cam 104 is rotated by a shaft 108, and the shaft 108 is rotated by a worm wheel 26 meshing with a worm 28 on the main drive shaft 30'.

The blank which is beyond the punch 97, and which is severed from the strip 12 by this final punching operation, is indicated by the reference character 12'. A post 112 is located at a mid point between the ends of the blank 12 and in contact with one side of the blank. There is a bending tool 114 on the other side of the blank, and this tool 114 has a recessed face 116 shaped to bend the blank 12' around the post 112 into the dotted line position shown in FIGURE 1.

The bending tool 114 slides in a guide way 118, and is advanced by a cam 120 on a shaft 122 with a worm wheel 126. This worm wheel is rotated by a worm 28 on the main drive shaft 30. The bending tool 114 is retracted by springs attached at one end to lugs 132 on the bending tool 114 and at their other ends to fixed anchors 134.

After the blank 12 has been bent around the post into the dotted line position shown in FIGURE 1, a second cam-operated tool is moved into contact with the left hand portion of the blank 12 to bend the blank around the upper left hand quadrant of the post 112. This bending tool 140 slides in a bearing 142 of a fixed frame.

A third cam-operated bending tool 145 slides in a bearing 146 and into contact with the right hand portion of the blank 12' to bend the blank around the upper right hand quadrant of the post 112. A fourth bending tool 150 slides in a bearing 152, and is moved into contact with the confronting end portions of the blank between the tools 140 and 145. The radial pressure from the tool 150 forces the dove tail projection 52 (FIGURE 2) into the dove tail groove 54 and thus secures the opposite ends of the blank 12 together. When using a tab and dove tail groove to connect the ends of the blank, a substantial pressure by the tool 150 is necessary because the tab 52 (FIGURE 2) is made slightly oversize with respect to the dove tail groove 54 in order to obtain a force fit.

FIGURE 7 shows the way in which the bending tool 114 exerts pressure against the blank 12' to bend it around the post 112. The tool 114 has a bottom lip 156 which holds the flange 75 to prevent it from straightening out as the blank 112 is bent around the post. Because of the stiffness of the metal of the blank 12', it is not necessary to shape the post 112 to fit the convex surface of the inside of the blank. The tool 114 has a center portion which contacts with the mid portion of the blank 12' to force it against the post 112 with suflicient pressure to give the blank 12' a curvature equal to the outside diameter of the post 112.

It is not necessary to have the post 112 undersize to allow for spring back of the blank 12' because when the ends of the blank are fastened together by the dove tail tab and groove, as previously explained, the blank 12 is held against any expansion.

The post 112 can be shaped to fit the inside surface contour of the blank 12 if desired, but it is preferred to have the post 112 with sidewalls that taper slightly to a smaller diameter at the lower end and without any extension of the post into the clearance with the blank 12 just above the flange 75. By having the straight taper, as shown in FIGURE 7, the formed thread protector can be stripped from the post 112 as soon as the tools are Withdrawn, by a stripper ring 160 which is pushed downwardly by operating links 162 when the time comes to strip the formed thread protector from the post 112.

FIGURE 8 shows the thread protector, which will be designated by the same reference character 12' as used for the blank, after the thread protector has been removed from the post. The confronting end faces of the metal form a seam 166, and the edges of this seam are permanently connected together by spot welds 168. If desired a continuous weld can be made along the whole length of the seam 116, or the seam edges can be brazed or otherwise bonded together. If the equipment is designed for the purpose, the spot welds 168 can be made while the thread protector 12' is on the post around which it is formed, but generally the spot welding is done after removing the thread protector from the post.

The final operation in the manufacture of the thread protector is the chasing of threads 172 (FIGURE 9) in the inside surface of the throat, This thread corresponds to the thread of the pipe on which the protector 12' is intended to be used. FIGURE 9 shows the pipe in phantom and the pipe is designated by the reference character 175. It will be noted that the flange 75 extends inwardly far enough to cover the end face of the pipe 175.

FIGURE 9 shows the thread protector with a seam 177 having no dove tail connection. This seam 177 is brazed and may be brazed while on the forming post, but preferably after removal from the post. If the seam edges spread after removal of the bending tools and the seam is not brazed until after removal from the post around which it is formed, then it is necessary to insert the thread protector in a clamp which brings the seam edges together again for brazing, welding or otherwise bonding them.

The dove tail tab 52 and cut-out 54 of the preferred construction has the outstanding advantage of providing a simple fastening for holding the seam together, and a fastening which can be made and connected automatically as a part of the automatic cutting, shaping and bending of the strip to form the thread protector as illustrated diagrammatically in FIGURES 1-7.

The preferred construction has been illustrated and described, but changes and modifications can be made and some features can be used in different combinations without departing from the invention as defined in the claims.

What is claimed is:

1. The method of making thread protectors, each of which has a flared entrance at one end, an inwardly extending flange at the other end, and a throat intermediate the ends, which method comprises feeding a continuous length of flat strip in successive steps each of which is equal to the length of strip required to make a protector, advancing different portions of the strip by one of said feeding steps in a substantially straight line to and through successive work regions and bringing a new length of the strip to a first work region, operating on diflerent portions of the strip while in said straight line and at the different work regions to form a flange extending lengthwise along one edge of the strip at one Working region, and to form a portion of the remaining height of the strip with a concavo-convex cross section extending lengthwise of the strip, advancing an end portion of the strip to a final bending station into positions to be operated upon by tools at said final bending station and while said end portion with its flanged edge and concavo-convex cross section remains attached to the rest of the strip, and with said end portion so positioned,

cutting it from the strip to form a separated blank in the final bending station, bending each successive blank in said final bending station in a direction with the flange extending inward, and holding the flange in its angular relation to the rest of the strip during said bending, and simultaneously with the operations at the other regions on the uncut strip, continuing the bending of the blank to a substantially circular shape with the opposite ends of the blank confronting one another at a seam of the thread protector, the bending being in a direction to leave the concove surface of the blank on the inside of the curve to form the throat for the thread protector, and the bending at the final bending station being performed by bringing forces against the blank at successive locations with the successive locations further along the blank toward the ends thereof, the forming, cutting and bending being performed at adjacent work regions and as part of a continuous mechanical process 2. The method of making thread protectors as described -in claim 1 and in which the strip is cut to form ends for the blanks prior to any other operations on the strip, but connections are left across the cuts and between the ends of successive blanks so as to maintain the continuity of the strip during subsequent operations, and the connecting portions are finally cut from the strip after the forming operations on the strip and before the bending of a blank to circular shape.

3. The method of making thread protectors as described in claim 1, and in which the opposite ends of the formed blank are connected together along at least a portion of the length of the seam between said ends, and the inside surface of the thread protector is then threaded with threads of a size to screw on the pipe with which the thread protector is intended to be used.

4. The method of making thread protectors as described in claim 1 and in which the strip is advanced with a step-by-step feed and the flange is formed by the application of pressure to the full length of a blank simultaneously and while the strip is stationary, and after the blank is advanced another step by the step-by-step feed, the concave-convex cross section is imparted to the strip by force applied simultaneously to the full length of the blank while the blank is stationary between feeding steps, and holding forces are applied to the flange in both a longitudinal and radial direction to prevent the flange from straightening out during the bending of the metal of the blank to a circular shape.

5. The method of making a thread protector having a flaring entrance with a smooth inside surface for receiving the end of the pipe on which the thread protector is to be used, and with a throat at the inner end of the diverging entrance, threads on the throat for screwing over the pipe and an enlarged diameter portion beyond the throat with clearance from the ends of the threads of the pipe on which the protector is screwed, which method comprises feeding a flat strip of hot-rolled steel to a first work station, cutting the strip at the first station to provide a dove-tail projection and a complementary dove tail groove on opposite sides of the cut and with the cut discontinuous along the height of the strip so that successive blanks produced by cuts at the different regions along the length of the strip are connected together in end-to-end relation, advancing the strip with a step-bystep motion in successive steps each of which is equal to the length of strip required to make a protector, applying reciprocating pressure to the strip between feeding steps and along the full length of a blank to form a flange along the entire length of one longitudinal edge of the blank, forming the strip at another work station by applying force which bends the strip above the flange to a concavo-convex cross section along the entire length of the blank, cutting the connection between successive blanks after the forming operations, bending each blank as it is severed from the strip to a circular shape and holding the flange in its angular relation to the rest of the strip during said bending, continuing the bending until the opposite ends of the blank confront one another along a seam, the bending being performed by maintaining resisting force against the inside of the bend and by applying radial forces inwardly at different angular locations successively around the circular contour to Which the blank is bent, bonding the seam edge together along at least a portion of the length of the seam, and then threading the throat of the protector to fit the threads of a pipe with which the protector is intended to be used.

6. The method of making a thread protector as described in claim 5 and in which the ends of the blank on opposite sides of the seam are locked together as a part of the bending operation and the seam is then permanently bonded by spot Welding at spaced regions along its length.

References Cited in the file of this patent UNITED STATES PATENTS Blakey Jan. 27, Schweinert et a1. Apr. 30, Cable Aug. 15, Shrum et a1. Aug. 23, Klocke Dec. 30, Engstrom Nov. 26, Keller Aug. 9, Borton Dec. 2, Kennedy Mar. 6, Clark Sept. 9, Peter et al. Feb. 22, Houck Sept. 11,

Ellzey Mar. 26, 

